1. Technical Field
The present invention relates to a vehicle occupant restraint. In particular, the present invention relates to a tether assembly for an inflatable vehicle occupant restraint such as an air bag.
2. Description of the Prior Art
An inflatable vehicle occupant restraint such as an air bag is used to restrain a vehicle occupant in the event of sudden deceleration such as occurs in a vehicle collision. A typical air bag includes fabric panels which define an inflation fluid volume. When inflation fluid under pressure is supplied to the air bag, the panels move apart from each other as the air bag assumes an inflated condition.
It is known to use tethers extending between the panels of an air bag to control the shape of the air bag when inflated. The tethers are typically straps of fabric material disposed inside the air bag and having opposite ends stitched to the air bag panels. When the air bag becomes fully inflated, the tethers extend fully and stop further movement of the panels away from each other. This places a sudden shock load on the tethers, on the panels, and on the stitching which joins the tethers to the panels.
The material of the air bag panels is typically thinner and lighter than the material of the tethers and the stitching material itself. Thus, the strength of the material of the air bag panels determines the maximum load that can be applied to the tethers. The highest load per unit area of panel material occurs where the panels are stitched to the tethers, as this is where the load is transmitted between the relatively strong material of the tethers and the weaker material of the panels.